The hydrogen and carbon which is not consumed by the oxygen in the blood, is seized upon by the liver, who employs it in the manufacture of bile. Therefore the greater the amount of unemployed hydrogen and carbon there is in the blood, the greater is the quantity of bile manufactured by the liver—that is all. When once the body has attained to its proper degree of heat, it is in vain you load it with combustibles; it will not get any warmer, do what you will. Only you will have cut out so much extra work for the liver, and the poor wretch will have to get through it as he can. Accordingly, what happens in the long run to our great eaters and drinkers, whether in India or elsewhere? The bile-manufacturer, overwhelmed with work, gets worn out at last, and kicks; and people come home with that miserable disease, which is called the "liver-complaint."
This is one explanation of that wonderful uniformity of temperature which, happily, human imprudence cannot disturb. But the blood has a second resource for getting rid of its superfluity of hydrogen and carbon, and herein especially is displayed the beautiful foresight with which everything about us has been prearranged. We are told that wolves, when they get hold of a larger piece of meat than they care to eat at the moment, carry off what they do not want to some corner and bury it in the ground, whence they get it again when their hunger returns. Dogs sometimes do the same; and the blood has a similar instinct. Listen attentively, for this is very interesting.
I light a candle and you see a bright flame, which will last as long as there is any tallow below the wick. Can you tell me what it proceeds from?
Nay, do not laugh at the question; it is quite to the purpose, I assure you.
We know, do we not, that the substances which burn best are those which are full of hydrogen and carbon? Tallow, then, is one of those substances. But tell me further, if you please, what is tallow?
Tallow is mutton fat, allow me to say, if you never heard it before.
Now comes the question, who provided the sheep's fat with such a quantity of hydrogen and carbon as to qualify it for making candles?
The sheep's blood undoubtedly, since blood is the purveyor-general of living bodies—of the sheep's body as well as of our own.
But how came it that the sheep's blood had so large a stock of these materials?
Undoubtedly, again, because there was more of them in the food the sheep had eaten than the oxygen was able to consume or the liver to employ. In short, the sheep has lungs and a bile-manufactory, as we have; oxygen performs the same office for it as for us. What takes place in its body in the matter of respiration is an exact counterpart of what happens in ours, and the history of its fat is simply the history of our own.